NAME

       nvramtool - read/write coreboot-related information

SYNOPSIS

       nvramtool [OPTS] [-n] -r NAME
       nvramtool [OPTS] -e NAME
       nvramtool [OPTS] -a
       nvramtool [OPTS] -w NAME=VALUE
       nvramtool [OPTS] -p INPUT_FILE
       nvramtool [OPTS] -i
       nvramtool [OPTS] -c [VALUE]
       nvramtool [OPTS] -l [ARG]
       nvramtool [OPTS] -d
       nvramtool [OPTS] -Y
       nvramtool [OPTS] -b OUTPUT_FILE
       nvramtool [OPTS] -B INPUT_FILE
       nvramtool [OPTS] -x
       nvramtool [OPTS] -X DUMPFILE
       nvramtool [OPTS] -v
       nvramtool [OPTS] -h

DESCRIPTION

       nvramtool  is  a  utility  for  reading/writing  coreboot  parameters and displaying information from the
       coreboot table.

       The coreboot table resides in low physical memory.  It is created at boot time by coreboot, and  contains
       various  system  information  such  as  the type of mainboard in use.  It specifies locations in the CMOS
       (nonvolatile RAM) where the coreboot parameters are stored.

       This program is intended for (x86-based) systems that use coreboot.  For information about coreboot, see
       https://www.coreboot.org/.

PARAMETERS

       [-n] -r NAME
              Show the value of the coreboot parameter given by NAME.  If -n is specified, show only the  value.
              Otherwise show both parameter name and value.

       -e NAME
              Show all possible values for parameter given by NAME.

       -a     Show the names and values for all coreboot parameters.

       -w NAME=VALUE
              Assign VALUE to coreboot parameter given by NAME.

       -p INPUT_FILE
              Assign  values to coreboot parameters according to the contents of INPUT_FILE.  The format of this
              file is described below.

       -i     This is similar to the -p option, except that the contents  of  the  input  file  are  taken  from
              standard input.

       -c [VALUE]
              If  VALUE  is present then set the CMOS checksum for the coreboot parameters to VALUE.  Otherwise,
              show the checksum value.

       -l [ARG]
              If ARG is present then show information from the coreboot table as specified  by  ARG.   Otherwise
              show all possible values for ARG.

       -d     Do a low-level dump of the coreboot table.

       -Y     Write CMOS layout information to standard output.  If redirected to a file, the layout information
              may be used as input for the '-y LAYOUT_FILE' option (see below).

       -b OUTPUT_FILE
              Write  the  contents  of  CMOS  memory  to  the  binary  file  OUTPUT_FILE.  The first 14 bytes of
              OUTPUT_FILE do not contain actual CMOS data, and are always written as zeros.  This is because the
              first 14 bytes of the CMOS area do not contain CMOS memory.  These bytes  are  involved  with  the
              functioning of the real time clock.

       -B INPUT_FILE
              Read  binary  data  from  INPUT_FILE  and  write  the  data to CMOS memory.  The first 14 bytes of
              INPUT_FILE are skipped and data is written to CMOS starting at the 15th byte  of  the  CMOS  area.
              This  is  because the first 14 bytes of the CMOS area do not contain CMOS memory.  These bytes are
              involved with the functioning of the real time clock.

       -x     Show a hex dump of all CMOS data.  The first 14 bytes of the dump do not contain actual CMOS data,
              and are always shown as zeros.  This is because the first 14 bytes of the CMOS area do not contain
              CMOS memory.  These bytes are involved with the functioning of the real time clock.

       -X DUMPFILE
              Read binary data from DUMPFILE (presumably a  CMOS  dumpfile  created  using  the  -b  OUTPUT_FILE
              option) and show a hex dump of the data.

       -v     Show version information for this program.

       -h     Show a help message for this program.

OPTIONS

       In all cases above, [OPTS] evaluates to the following:

           [-y LAYOUT_FILE | -t]

       The  '-y  LAYOUT_FILE'  option  tells  nvramtool  to  obtain CMOS layout information from the contents of
       LAYOUT_FILE.  Likewise, the '-t' option tells nvramtool to obtain CMOS layout information from  the  CMOS
       option  table  (contained  within  the  coreboot table).  If neither option is specified, the CMOS option
       table is used by default.  LAYOUT_FILE follows the format of the cmos.layout files provided by coreboot.

       If the coreboot installed on your system was built without specifying CONFIG_HAVE_OPTION_TABLE, then  the
       coreboot  table  will not contain a CMOS option table.  In this case, the '-y LAYOUT_FILE' option must be
       used.

       These two options are silently ignored when used in combination with  other  options  (such  as  -h,  for
       instance) for which they are not applicable.

FILE FORMAT

       For  the  -p option, INPUT_FILE must consist of a sequence of lines such that each line is either a blank
       line, a comment, or an assignment.  A blank line consists only of  zero  or  more  whitespace  characters
       (spaces and tabs).  A comment is constructed as follows:

           [ws]#[text]

       Here,  [ws] indicates optional whitespace characters and [text] indicates optional text.  Blank lines and
       comments are both ignored.  An assignment is constructed as follows:

           [ws]NAME[ws]=[ws]VALUE[ws]

       Here, NAME is the name of a coreboot parameter and VALUE is the value that  will  be  assigned  to  NAME.
       VALUE  is  allowed  to  contain  whitespace  characters,  but  it  must  begin and end with nonwhitespace
       characters.  Note that each comment must appear on a line by itself.  If you attempt to add a comment  to
       the end of an assignment, then the comment will be interpreted as part of VALUE.  It is useful to observe
       that  the  output  produced  by both the -a and the '[-n] NAME' options (without -n specified) adheres to
       this file format.

BUGS

       This program does not implement any type of synchronization to  ensure  that  different  processes  don't
       stomp  on  each other when trying to access the nonvolatile RAM simultaneously.  Therefore, corruption of
       the BIOS parameter values may occur if multiple instances of this program are executed concurrently.

AUTHORS

       David S. Peterson <dsp@llnl.gov> <dave_peterson@pobox.com>
       Stefan Reinauer <stepan@coresystems.de>

                                                 September 2008                                     NVRAMTOOL(8)